Audio capture float format using ALSA - cannot set format - audio

Question

I'm trying to capture audio using Alsa and c/c++ library. I'm able to do it successfully using 16bit and 32bit Int but when I try to use floating point formats I'm not able to set the corresponding formats.
example:
//returns -22 and doesn't work
err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_FLOAT));
//returns 0 and work as expected.
err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_S32));
I've been searching for quite a while an I simply did not found an answer for this problem.
Thank you in advance!
Full code:
#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
int main(int argc, char *argv[]) {
int i;
int err;
char *buffer;
int buffer_frames = 128;
unsigned int rate = 44100;
snd_pcm_t *capture_handle;
snd_pcm_hw_params_t *hw_params;
snd_pcm_format_t format = SND_PCM_FORMAT_FLOAT;
//snd_pcm_format_t format = SND_PCM_FORMAT_S32;
if ((err = snd_pcm_open(&capture_handle, "hw:0", SND_PCM_STREAM_CAPTURE, 0)) < 0) {
fprintf(stderr, "cannot open audio device %s (%s)\n",
argv[1],
snd_strerror(err));
exit(1);
}
fprintf(stdout, "audio interface opened\n");
if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
fprintf(stderr, "cannot allocate hardware parameter structure (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params allocated\n");
if ((err = snd_pcm_hw_params_any(capture_handle, hw_params)) < 0) {
fprintf(stderr, "cannot initialize hardware parameter structure (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params initialized\n");
if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
fprintf(stderr, "cannot set access type (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params access setted\n");
if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, format)) < 0) {
fprintf(stderr, "cannot set sample format (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params format setted\n");
if ((err = snd_pcm_hw_params_set_rate_near(capture_handle, hw_params, &rate, 0)) < 0) {
fprintf(stderr, "cannot set sample rate (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params rate setted\n");
if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, 2)) < 0) {
fprintf(stderr, "cannot set channel count (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params channels setted\n");
if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
fprintf(stderr, "cannot set parameters (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "hw_params setted\n");
snd_pcm_hw_params_free(hw_params);
fprintf(stdout, "hw_params freed\n");
if ((err = snd_pcm_prepare(capture_handle)) < 0) {
fprintf(stderr, "cannot prepare audio interface for use (%s)\n",
snd_strerror(err));
exit(1);
}
fprintf(stdout, "audio interface prepared\n");
buffer = (char*) malloc(128 * snd_pcm_format_width(format) / 8 * 2);
fprintf(stdout, "buffer allocated %d\n", snd_pcm_format_width(format) / 8 * 2);
int fd = open("in.pcm", O_CREAT | O_RDWR, 0666);
//for (i = 0; i < 10; ++i) {
i = 0;
while (++i) {
//snd_pcm_wait(capture_handle, 1000);
if ((err = snd_pcm_readi(capture_handle, buffer, buffer_frames)) != buffer_frames) {
fprintf(stderr, "read from audio interface failed (%s)\n",
snd_strerror(err));
exit(1);
}
write(fd, buffer, 128 * snd_pcm_format_width(format) / 8 * 2);
//fprintf(stdout, "read %d done\n", i);
}
close(fd);
free(buffer);
fprintf(stdout, "buffer freed\n");
snd_pcm_close(capture_handle);
fprintf(stdout, "audio interface closed\n");
exit(0);
}